The present invention relates to a printing device to be connected to a host computer, such as a personal computer.
Generally, the printing device receives print data every data unit from a host computer, e.g., a personal computer, and renders a reception process completion signal active every time it receives the unit data and waits for the next data delivered from the host computer. The host computer, which sends print data every data unit to the printing device, does not send the next data till the reception process completion signal becomes active. In other words, the host computer sends print data to the printing device every time a reception process completion signal received from the printing device becomes active.
Recent printing devices are operable at high speed. Accordingly, if the printing device quickens the timing of making the reception process completion signal active in accordance with the data transferring ability of the host computer, the host computer successively sends print data at a data transfer rate, which depends on its data transfer ability. In other words, if the host computer is able to transfer data at a high transfer rate, it is allowed that the printing device renders the reception process completion signal active at instant that the printing device completes the reception of the print data. On the other hand, if the host computer is unable to transfer data at a high transfer rate, the printing device waits for a time, which depends on the data transfer ability of the host computer, after it completes the reception of print data, and then renders the reception process completion signal active. For this reason, the printing device switches by necessity the timing of rendering the reception process completion signal active (width of the reception process completion signal) to another timing in accordance with the data transfer ability of the host computer. The Unexamined Japanese Patent Application Publication No. Hei. 5-313836 (prior device 1) discloses a printing device capable of transferring data in harmony with the data transferring ability of the host computer connected thereto in a manner that the time width of the reception process completion signal is set to a desired value of width in a parallel interface circuit for receiving print data from the host computer.
The Unexamined Japanese Patent Application Publication No. Hei. 7-148991 (prior device 2) discloses a printing device capable of transferring data in harmony with the data transferring ability of the host computer connected thereto in a manner that the time width of the reception process completion signal is switched to a desired value of width in a parallel interface circuit for receiving print data from the host computer.
The Unexamined Japanese Patent Application Publication No. Hei. 5-150914 (prior device 3) discloses a printing device arranged such that a plural number of parallel interface circuits for receiving print data from the host computer are provided, time width information of a reception process completion signal is stored for each parallel interface circuit, and the printing device carries out a data transfer which depends on the time information of the parallel interface s elected .
The Unexamined Japanese Patent Application Publication No. Hei. 4-328934 (prior device 4) discloses a printing device arranged such that when an emulation mode is switched, communication conditions are automatically set to proper ones in the parallel interface circuit for receiving print data form the host computer.
Each of the conventional devices (prior devices 1 to 3) can transfer data at a transfer rate, which depends on the data transferring ability of the host computer by switching or setting the time width of the reception process completion signal. The setting or switching of the time width of the reception process completion signal necessitates manual operations by a user through the keyboard or the host computer connected to the printing device, however. Further, the knowledge and information on the host computer are indispensable for the checking as to if the data transfer between the host computer and the printing device is proper after the time width of the reception process completion signal is altered.
In the prior device 4, when the emulation mode is switched and the communication conditions are altered, the printing device analyzes receiving data to automatically switch the emulation mode to a proper one. No intervention by the user is required for this operation. In the device design, no consideration given on the checking as to if the data transfer between the host computer and the printing device is proper after the time width of the reception process completion signal is altered. Because of this, the knowledge and information on the host computer are indispensable for the setting of communication conditions. Further, in the case of the printing device which is designed lacking the automatic switching function of the emulation mode, the user's intervention is essential to the altering of the communication conditions.
The prior devices suffer from an additional disadvantage. Information storing means is indispensable for the retaining of the time width information of the reception process completion signal every the altering of the communication conditions. To this end, information storing means is provided in the parallel interface or an independent storing means is provided. This problem is more serious in particular in the printing device having a number of parallel interfaces since its circuit scale is large.
Thus, the high data transfer ability of the host computer is uncertain. Because of this, the time width of the reception process completion signal of the printing device is generally selected so as to be compatible with such a host computer that cannot transfer data at a high data transfer rate. This necessitates the user's intervention for high speed data transmission. Also when the printing device is connected to the host computer that can transfer data at a high data transfer rate, an intervention by the user who has the knowledge and information on the host computer is required for the communication condition setting. Further, every time the host computer is changed to another, it is necessary to check as to if the high speed data transmission is required.